Israel Medical Association Journal

Between the 1960s and 1980s, the main focus of biological research was nucleic acids and the translation of the coded information into proteins. Protein degradation was a neglected area and regarded by many as a scavenger, non-specific and end process. While it was known that proteins are turning over, the large extent and high specificity of the process - where distinct proteins have half-lives that range from a few minutes to several days - have not been appreciated. The discovery of the lysosome by Dr. Christian de Duve did not change this view significantly, as this organelle is involved mostly in the degradation of extra- and not intracellular proteins, and it was clear that lysosomal proteases, similar to those of the gastrointestinal tract, cannot be substrate specific. The discovery of the complex cascade of the ubiquitin pathway has changed this view dramatically. It is now clear that degradation of cellular proteins is a highly complex, temporally controlled, and tightly regulated process that plays major roles in a broad array of basic pathways during cell life and death. With the multitude of substrates targeted and processes involved, it is not surprising that aberrations in the pathway have been recently implicated in the pathogenesis of many diseases, certain malignancies and neurodegeneration among them. Degradation of a protein via the ubiquitin pathway involves two successive steps: a) conjugation of multiple ubiquitin moieties to the substrate, and b) degradation of the tagged protein by the downstream 263 proteasome complex with release of free and re-utilizable ubiquitin. Despite intensive research, the unknown still exceeds what we currently know on intracellular protein degradation and major key problems remain unsolved. Among these are the modes of specific and timed recognition of the myriad substrates of the system and the nature of the mechanisms that underlie aberrations in the system and pathogenesis of diseases.

Background: Case-control and prospective studies indicate that an elevated plasma homocysteine level is a powerful risk factor for atherosclerotic vascular diseases. Certain medications can induce hyperhomocystinemia, such as methotrexate, trimethoprim and anti-epileptic drugs. There are few reports indicating an interaction between lipid-lowering drugs (cholestyramine and niacin) and homocysteine. Recently, an interaction was shown between fenofibrate and benzafibrates (a fibric acid derivative) and homocysteine plasma levels.

Objectives: To evaluate the effects of different fibrates on plasma homocysteine levels and to measure the reversibility of this effect.

Methods and Results: We investigated the effects of ciprofibrate and bezafibrate on homocysteine levels in patients with type IV hyperlipidemia and/or low high density lipoprotein levels. While a 57% increase in homocysteine was detected in the ciprofibrate-treated group (n=26), a 17% reduction n homocysteine was detected in the group treated with bezafibrate (n=12). The increase in homocysteine in the ciprofibrate-treated group was sustained for the 12 weeks of treatment and was partially reversible after 6 weeks of discontinuing the ciprofibrate therapy.

Conclusions: These results indicate that an increase In plasma homocysteine levels following administration of flbrates is not a class effect, at least in its magnitude. Moreover, it is reversible upon discontinuation of the treatment.
 

Background: Information is lacking on the effects of hormone replacement therapy in women with diabetes, especially during moderate chronic hyperglycemia.

Objectives: To study the effects of HRT on the lipid profile and the low density lipoprotein subclass distribution in women with type 2 diabetes under satisfactory and non-satisfactory glycemic control.

Methods: Fifty-four postmenopausal women after a 6 week run-in diet were randomized to receive either placebo(HbAlc <8%, n=13 HbAlc >8%, n=17) or HRT (HbAlc<8%, n=11 HbAlc >8%, n=13) for 12 weeks. HRT consisted of cyclical conjugated estrogens 0.625 mg/day plus medrogestone 5 mg/day. At the beginning and at the end of each treatment period the LDL subclass distribution was estimated by density gradient ultracentrifugation.

Results: At the baseline and during the study, the HbAlc level was significantly higher in hyperglycemic patients than in the near-normoglycemic controls (baseline 10.2±2.9 vs. 6.5±0.7%, P<0.01). They showed a trend for higher total and LDL cholesterol, triglycerides and lower high density lipoprotein-cholesterol compared to near-normoglycemic con­trols, as well as significantly higher triglyceride concentrations in very low density lipoprotein, intermediate density lipoprotein and LDL-1 particles and cholesterol content in LDL-1 and -2 particles. HRT decreased LDL-cholesterol in both groups. In the normoglycemic patients a small increase in HbAlc was observed (6.5±0.7 vs. 7.4+1%, P=004). In all cases, HRT did not modify the proportion of LDL represented by denser LDLs.

Conclusions: HRT did not modify the LDL subclass distribution, even in the presence of moderate chronic hyperglycemia in women with type 2 diabetes.

Background: inflammation is an important feature of atherosclerotic lesions and increased production of the actuephase reactant. The contribution of coagulation factor to the development of coronary artery disease has not yet been clearly established.

Objective: To test whether C-reactive protein, fibrinogen and antithrombin-III are associated with angiograpic CAD, history of myocardial infarction and extensive atherosclerotic involvement.

Methods: Blood samples were tested for CRP, fibrinogen and AT-III levels from 219 individuals undergoing coronary angiography.

Results: CRP was higher in patients with CAD (0.95 + 1.31, n=180, vs. 0.39 + 0.61 mg/dl, n=39, P<0.0001) and in those with a history of MI (1.07 + 1.64, n=96, vs. 0.65 + 0.72 mg/dl, n=84, P<0.05) than in control subjects. The patients who developed unstable angina had higher CRP levels than the patients with stable CAD (2.07 + 2/38, n=7, vs. 0.80 + 1.13 mg/dl, n=173, P<0.001).

Fibrinogen was significantly higher in patients with CAD (298 + 108 vs. 258 + 63 mg/dl, P<0.01). In patients with CAD, mean AT-III value was less than in patients without CAD, but this difference was found in CRP, fibrinogen and AT-III values among the patients with single, double or triple vessel disease.

Conclusion: CRP is elevated in patients with CAD and a history of MI. Elevated levels of CRP at the time of hospital admission is a predictive value for future ischemic events.

There is an association between higher levels of fibrinogen and CAD. The association of AT-III levels with CAD needs testing in further studies.
 

Background: Dyslipidemia and obesity serve as risk factors for the development of atherosclerotic cardiovascular disease. Fasting is sometimes recommended for treating these conditions. This study was undertaken to try to resolve conflicting results reported in the literature.

Objectives: To study the effect of fasting (0 calories, with free intake of fluids) for 3-5 days on plasma concentration of triglyceride, cholesterol and apolipoprotein B.

Methods: Physicians, about to begin a hunger strike, were divided into four groups: normolipidemic non-obese men (group 1), two moderately obese men and two men with type IV hyperlipidemia (group 2), healthy non-obese women (group 3), and healthy non-obese women on oral contraceptives (group 4). Adherence to fasting was monitored daily by detailed interviews, loss of weight, drop in plasma glucose, presence of ketonuria, progressive rise in serum creatinine and uric acid, and decrease in plasma pH. We monitored their serum glucose, electrolytes, liver function, lipids, lipoproteins and apolipoprotein B on days 0, 3, and 5.

Results: Physicians who adhered to complete fasting lost more than 1.5% of their body weight after 3 days of fasting (n=12), and more than 3.2% at 5 days (n=5). All non-obese normolipidemic males and females (groups 1 and 3) showed an increase in plasma triglyceride (by 28-162%) and very low density lipoprotein cholesterol (by 22-316%) after 3 days of fasting. The obese and hyperlipidemic men (group 2) showed a decrease of 17-63% in their VLDL cholesterol, and the women on oral contraceptives (group 4) showed a 20% decrease in their plasma triglyceride on day 3. Low density lipoprotein cholesterol increased by 13% in group 2, decreased by 7.3% in group 4, and remained unchanged in group 1 and 3. Apolipoprotein B level correlated well with LDL cholesterol in all groups. High density lipoprotein cholesterol changes were inconsistent.

Conclusions: These results help to explain and reconcile previous published reports. The metabolic background of the individual together with the amount of energy consumed affect the behavior of plasma lipids and lipoproteins levels during fasting.

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VLDL= very low density lipoprotein

LDL= low density lipoprotein
 

Background: Previous reports on the behavior of procalcitonin blood levels in diverse clinical conditions suggest that it is part of the activation of cellular immunity and is another acute-phase reactant.

Objective: To compare procalcitonin with C-reactive protein, a well-known acute-phase reactant, in a series of acutely febrile pediatric patients and to review recent literature on procalcitonin.

Methods: Procalcitonin and CRP levels were evaluated in 38 blood samples of pediatric patients who were admitted to the Dana Children’s Hospital for evaluation of unexplained fever or for sepsis work-up.

Results: The parallelism between procalcitonin and CRP was found to be highly significant (P<0.01).

Conclusion: The rise of procalcitonin blood levels in febrile pediatric patients suggests that it is part of the acute-phase reaction, parallel with the CRP reaction.